It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
If you take an average dynamic web site, what would be peak number of users that one small ec2 instance could serve concurrently. Please don't send "it depends..." answers, I need some crudest estimation. Thanks.
Well... it depends! :) I am sure you are able to serve really a lot of static images with a high performance webserver like nginx. But you will only be able to serve a small number of users if you have a complete Java enterprise stack.
There are so many factors in this that you can not give at least the crudest estimation. Some points to consider is your app, the processing it does, how many resources it needs, your server infrastructure... too many variables to give a correct answer.
Therefore I suggest the following: develop a comparable set of test tools. Try to mimic the load pattern of your users as close as possible (it would for example be possible to replay an Apache access log). Measure how many requests you will be able to serve. Tune your config, measure again. Change servers, measure again. This is the only way to get any results.
Tools include Siege, multi-mechanize, ab and probably a lot more.
Related
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I want to digitise some places of my city in ArcGIS. I found ArcGIS 'World Imagery' layer which I can use it as a basemap for digitisation. But the problem is it works only while the internet is connected. Is there anyway to save the cache of the layer at a particular zoom level so that I can work on it offline even after I restart the computer.
If no, please tell me any other way- may be with google or bing imagery, I need to digitise important features of the city. So i require resolution at house level.
A quick and dirty way would be to take a screen shot, save it, add it as data, then georeference it with the "Georeferencing" toolbar. I'm not sure how to save a cache or how much memory that might take. If you are working at a fixed scale and can find the imagery you need (like google or bing), then take a screenshot or maybe use a program like Snagit (if you have it) to capture the extent you want at the best resolution.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
Do we really need a caching layer when using a nosql datastore? I understand the use case when using a traditional sql db, the overhead of query processing can be avoided by a simple key/value lookup. But in the case of nosql, that's not the case anymore. Also, the cache instances are almost always running in separate instances, which means they still have the same network delay associated with accessing a nosql datastore.
Thanks!
Caching is simply a tool for performance optimization and should be treated as such. This means doing some load testing to see what gains (if any) your performance enhancements give.
Most NoSQL servers do make claims to be much faster than traditional RDBMS but only testing it out will tell you if they're faster for your applications and infrastructure.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I've a book review site, where readers can write reviews about books, other users can post comments. I wanted to know following things automatically whenever new review publish or new comment published.
(1) whether book review is positive or not? How much % positive / negative?
(2) whether comment made by particular user is positive or not? How much % positive / negative?
(3) I want to read Tweets about particular book and wanted to check whether the tweet is positive or not?
bottom line, I want some tool suggestions (opensource), which I can use for my website. Website is written in PHP and I'm looking for some semantic analysis tool which I can customize to meet my need or which best fit my need.
if not, I want to know if its easy to build one with minimal requirements. I know PHP, Perl, Shell Script. I can learn Python. I know C++, Java may be right language to start from scratch; but don't have much experience.
There is an open source semantic analyses engine incubated in the Apache Software Foundation, currently, called Stanbol. It provides APIs to interface with it over HTTP as well as through a Java API if needed. It's pretty advanced, but generally speaking if your needs are simpler you can always try some SaS solution like uClassify.
In response to your first request, I'd suggest you create a form where the user has a voting option (such as a x/5 star rating, etc) then you would calculate the average from all of the reviews.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 10 years ago.
I am working on a pricing platform on wich I have to implement a distributed rate limiting algorithm. I have k gateways that provide x services. Any gateway can provide any service (via a load balancer). A customer buy a number of call per second to a service, its call could be routed through any gateway. So, is somebody knowing a good algorithm to update call counters on all gateways in order to limit customer calls?
Two important indicators, regarding this algorithm, are the network overhead and the deviation between the number of accepted calls and the rate limit.
Thanks!
Edit
I just want to know if there is a "well-known" algorithm.
I've implemented a solution based on this article (archive.org). I think the algorithm is called Leaky Bucket but it works fine. It's not perfect since it allows the entire quota to be used in a burst, but overall it's very fast with node.js and Redis. The difference between accepted requests and rate can be quite high and depend on the ratio between sample window and bucket size.
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 11 years ago.
My multicore machine is receiving packets and distributes them evenly (sort-of round robin) among its cores. Each core should decide whether to let the packet pass or drop it, depending solely on its origin address.
I need to find lock-less algorithm and data structure to allow this. Can you help?
If you are happy to use Java, or look at the design of Java source, you could chose a random key and then retrieve a queue from http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/ConcurrentHashMap.html. Given the queue, you could add the packet to it without blocking if it was a http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/ConcurrentLinkedQueue.html
Much of java.util.concurrent is due to Doug Lea, who has information on it at http://gee.cs.oswego.edu/dl/concurrency-interest/index.html.
Possibly overkill for your particular problem, but might satisfy a general request for info on data structures in this area.